Alert on after 2nd coolstore blast

The Labour Department has issued a hazard alert after a refrigeration technician was burnt by exploding hydrocarbon-based refrigerant in circumstances disturbingly similar to the fatal Icepak Tamahere blast.

In the May incident the technician was burnt on his face and hands doing maintenance on a coolstore refrigeration unit that both he and the owner thought contained non-flammable R22 gas, known as Freon, when the system actually contained a flammable hydrocarbon-based refrigerant.

As at Tamahere, there were no signs to identify the refrigerant or its flammable hazard type, and the system was not designed to be charged with a hydrocarbon refrigerant, a Labour Department investigation found.

The Labour Department, which said the incident bore “some disturbing similarities to the coolstore fire at Tamahere in 2008 and therefore is seen as extremely serious,” described what happened.

The technician was contracted to repair a valve on the refrigeration unit’s evaporator inside the coolstore. The valve’s markings stated that the refrigerant used in the system was R22.

The system was pumped down, isolating the bulk of the refrigerant to the main plant situated outside the building. The technician climbed approximately five metres up a ladder to access the valve and began replacing it, which involved welding around the valve area. The welding generated heat, which in turn caused a rapid expansion of the residual refrigerant inside the system. The refrigerant ignited, causing a rapidly expanding ball of fire to erupt from the system directly into the technician’s face. He slid down the ladder to avoid further injury as the fireball rose to the coolstore’s ceiling.

This incident caused significant damage to the refrigeration plant and equipment.

The investigation also found:

No records were available to determine what the system had been charged with when commissioned. No subsequent records were available to suggest that the system had been retrofitted to operate using a hydrocarbon refrigerant.

The owner of the plant and the technician believed that the system was safe and that it complied with all relevant legislative requirements.

The refrigeration unit had been installed eight to ten years ago and had not required servicing subsequent to installation involving the refrigerant.

The type of refrigerant used did not contain a stenching agent; therefore it was difficult to determine if a leak occurred. As a result, there was the potential for the coolstore to be filled with a flammable gas which could remain undetected until a source of ignition was introduced.

In the alert, the Labour Department recommended that “employers, owners, persons in control of cool stores should immediately determine the substance their refrigeration unit/s are charged with. Where the system has been charged with a hydrocarbon refrigerant, they should determine if the system is suitable for that substance, having regard to the practical limit requirements as per the Australian/New Zealand Standard 1677.2:1998.

In a story reporting the incident, NZ Professional Firefighters Union vice president and Hamilton local president Peter Hallett told the Waikato Times the union had repeatedly asked the department exactly who was using the gas after the explosion at Icepak.

“We got told [after Tamahere] that an investigation by the department would involve any other plant using it … you would have to question the robustness of that investigation.”

Mr Hallett said that since the company had no knowledge the gas was being used, it must have been installed by a “rogue engineer”.

“There’s obviously people out there … installing this stuff and the occupants of the premises don’t know what’s in them.”

Institute of Refrigeration, Heating & Air Conditioning Engineers president Rodger Wyatt did not know about the May explosion, but was not surprised. “This is something that I have feared for some years … really there is no way of knowing what the cocktail inside the [refrigeration] system is.”

The Labour Department produced a fact sheet on the safe use of hydrocarbon refrigerants following the Icepak Tamahere explosion. Click the following link to download it (pdf) DOL hydrocarbon refrigerant fact sheet